File photo. Lane Turner/The Boston Globe via Getty Images(KAUFMAN, Texas) -- The Aryan Brotherhood, a white supremacist prison gang, has become one of the top focuses of authorities investigating the murders of two Texas prosecutors, sources told ABC News.

Prosecutors from Kaufman County, Texas, had helped imprison dozens of Aryan Brotherhood members late last year, the sources said.

In recent weeks Kaufman County District Attorney Mike McLelland and his top assistant Mark Hasse were murdered in shootings that have left investigators hunting for clues.

Cops are poring over hundreds of old cases that Hasse and McLelland prosecuted and following clues that involve not just the Aryan Brotherhood of Texas, but Mexican drug cartels, local drug traffickers and other violent individuals.

But they are aggressively pursuing a possible Aryan Brotherhood link, sources said.

In November, 34 suspects associated with the Aryan Brotherhood of Texas were indicted on federal racketeering, murder and drug conspiracy charges. Ten members potentially faced the death penalty as prosecutors accused them of ruthless violence, including ordering hits on rival gang members.

A review of the case shows that the Kaufman prosecutors assisted in the investigation, along with more than a dozen agencies.

In December, Texas authorities sent out a bulletin warning that the group might seek retaliation because of the crackdown, sources said.

Authorities are also working to determine if the Texas killings are related to the March shooting death of Colorado prisons chief Tom Clements, gunned down at home. The chief suspect in the murder is ex-con Evan Ebel, an alleged member of a Colorado white supremacist prison gang known as 211.

Ebel had a swastika tattoo on his stomach and lightning bolt tattoos on his hands and wrists, along with the phrase "White Pride" on his arms, according to prison records released Tuesday.

Ebel was killed in a gun battle with Texas cops 100 miles from Kaufman County, just days after Clements' murder.

Authorities want to know why Ebel came to Texas and whether he has any associates in the Aryan Brotherhood of Texas, sources said.

As hundreds turned out to memorialize the McLellands Tuesday, authorities released new details of their deaths. Mike McLelland, who was known to carry a gun regularly in the weeks after Hasse was killed, was shot more than a dozen times.

Police are working to determine who made cellphone calls in the vicinity of the McLellands' home in the moments before the shooting, in the hopes that someone stands out as a possible suspect.